Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, CO.
Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA.
J Neuroimaging. 2020 Sep;30(5):587-592. doi: 10.1111/jon.12776. Epub 2020 Aug 30.
Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass.
Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature.
Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels.
Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.
颅外-颅内（EC-IC）手术旁路可改善颈动脉闭塞患者的脑血流（CBF）和脑血管反应性（CVR）。旁路移植血管通畅性以及移植物对术后 CVR 增加的贡献很难评估。本研究旨在评估 4D 流磁共振成像（MRI）评估 EC-IC 旁路前后颞浅动脉（STA）旁路移植血管通畅性和血流增强的效果。
连续 3 例颈动脉闭塞患者接受 EC-IC 旁路手术，分别在术前和术后使用 CVR 测试，通过术前和刺激后 4D 流-MRI 评估旁路移植物和颅内血管。
术前，2 例患者（患者 1 和 3）均未增加任何一侧的 STA 血流。第 3 例患者在数字减影血管造影（DSA）上有广泛的原位 EC-IC 侧支循环的证据，术前通过 STA 增加了血流（CVR = 1）。术后，所有患者旁路侧 CVR > 1。术前 CVR > 1 的患者术后移植血管的静息血流增加最大（从 40 至 130 mL/min），但刺激后 CVR 最小，为 160 mL/min（CVR = 1.2）。术前未显示移植物血流增加的 2 例患者术后分别增加了 10-20 和 10-80 mL/min（CVR = 2.0 和 8.0）。同时检测颅内血流。术后立即旁路后，2 例患者所有检测血管的静息血流速度均有轻度下降。在术后第 48 天进行 CVR 测试的患者，大多数颅内血管的血流速度稳定或增加。
4D 流 MRI 可在 CVR 测试期间进行非侵入性、同时检测颅内和颅外动脉血管，揭示了脑血管生理学中的独特模式。观察这些血流模式可能有助于改善患者选择，并为接受 EC-IC 旁路手术的患者提供更详细的术后评估。
